The use of elastomeric products in various suspension and anti-vibration applications is common and well known in the art.
One kind of commonly used suspension products are elastomeric springs. Elastomeric springs are generally used to achieve the best possible ride comfort in various kinds of vehicles. The elastomeric spring generally consists of an elastomeric body shaped in order to exhibit the desired damping characteristics.
One other kind of commonly used suspension products are diaphragms. The diaphragm is a bag or bellow filled with air. The shape and size of the air bellow can be different in order to adapt the damping characteristics. Also the pressure in the air bellow can be changed in order to change the damping characteristics.
One example of common anti-vibration products is anti-vibration mounts. The anti-vibration mounts generally consist of rigid plates or brackets with an elastomeric body placed in between. One of the rigid plates or brackets is then generally fastened to the vibration source, e.g. an engine, and the other, to the environment that shall be isolated from the vibrations, e.g. a vehicle or a vessel.
One problem associated with the above-mentioned suspension and anti-vibration products is the unfavourable burning characteristics. The elastomeric body of the products is generally manufactured from synthetic polyisoprene and natural polyisoprene comprising reinforcement substances. The synthetic and natural polyisoprene is flammable as well as several of the reinforcement substances, e.g. carbon black, mineral oil or other organic chemicals. This results in an elastic body that provides no inherent resistance to fire.
Elastomeric bodies of isoprene compounds are relatively easy to ignite and lead to rapid and hot fires. The fire can even consume small sections of the elastomeric body. During the fire heavy sooty black smoke is emitted in large quantities. This is a problem especially in applications where a fire or smoke emission can cause serious damage to people and/or equipment. When the products are used in confined compartments, like subways and machine rooms of naval vessels, smoke emissions and heat release is a serious problem, shortening the time that can be effectively used for an evacuation.
It is known to modify isoprene and natural rubber elastomeric products with halogenated flame-retardants. This approach does however improve the flame retardant characteristics of the product in question, but does also have several drawbacks. The halogenated flame retardant does for example increase the toxicity of the product. Many halogenated flame retardants have also been banned from use, due to environmental reasons.
Another known approach is to modify isoprene and natural rubber elastomeric products with non-halogenated flame-retardants. In this case it is common to use aluminium trihydride and magnesium hydroxide to improve the fire retardant characteristics. These substances must however be compounded into the elastomeric material with a high percentage, exceeding 50% of weight, to become efficient. By incorporating a flame retardant material to such an extent, the elastomeric material will start losing its key characteristics such as compression set, dynamic modulus and creep.
Yet another approach when trying to avoid risks related to fire of elastomeric products is to simply manufacture the elastomeric products in another material. One possible solution is to use a halogenated polymer in order to create a product with improved fire retardant characteristics. However, also in this case, the material will become toxic and less favourable. It is also possible to use non-halogenated polymers, e.g. silicone. These polymers are however more expensive and suffer from low physical strength.
In order to be able to use standard elastomeric products it has been proposed to coat the products with standard intumescent coatings such as those used in the construction industry. These coatings are however unsuitable for elastomeric products, due to the fact that they are not sufficiently elastic to remain on an elastomeric product, when the product is subjected to frequent and continuous surface elongation.